1. Field of the Invention
The present invention relates generally to interferometry, and specifically to a monolithic, spatially-separated, common-path interferometer.
2. Description of the Related Art
Interferometry has applications in many fields where precise measurement of movement is necessary. Fields using interferometry include aerospace, semiconductors, and general metrology.
Traditionally, interferometers utilize polarizing beam splitters to separate a measurement beam from a reference beam. The measurement beam is then reflected off a measuring object and the reference beam off a fixed reference object. Subsequently, when the polarization separated beams are mixed together, the beams interfere with each other, creating an interference pattern or an interferogram. Such interferograms are extremely sensitive to relative changes in the paths of the measurement beam and the reference beam. Thus, a precise measurement of changes in distance can be made by measuring changes in the resulting interference pattern signals of an interferometer.
Polarization-separated interferometers, however, suffer from polarization leakage, which can introduce errors and limit the measurement resolution to approximately 1 nanometer. Existing interferometers are also large, complex devices that are cumbersome to deploy and difficult to align. In addition, they suffer from various mechanical, thermal, and optical variations within the many components that make up the interferometers.